I have a single pole switch on a wall that turned on a ceiling light. I want to replace this ceiling lamp with a fan/light combo. I also want to replace the single switch to double switches (so I can control the fan and the light separately)

Here is what I see when I open up the switch box with the single pole switch:

Essentially, all the blacks are connected together, and the whites are connected together.

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Oh, and just off hand, unless you run an extra cable from the light switch to the ceiling fan, you won't be able to do it.
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cdeJul 12 '13 at 22:23

There needs to be enough cabling to wire two independent circuits. Unless it was planned out and two wires run from the junction box to the ceiling, you would need to add that in.
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cdeJul 12 '13 at 22:29

Why don't you get a ceiling light/fan combo with in-built pull cords for both light and fan. Job done.
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Andy akaJul 12 '13 at 23:15

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Many fans sold today have remote controls for fan and light functions, you only need to supply unswitched power to the fan. With some fans, a wall switch controlled light is not even a possibility. Find out what options your fan of choice offers before altering your house wiring.
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bcworkzJul 13 '13 at 22:43

@bcworkz Excellent point. Remotes offer several advantages and some can be surface mounted to act like a wall switch.
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bibJul 14 '13 at 3:19

1 Answer
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I am assuming that the upper wire is the cable that goes to the ceiling where the fan/light is to be installed. If so, you should have a red wire in the ceiling box that is unused and probably capped with a wire nut.

Your description of the switch box seems a little off. If all three black wires were connected together, what wires go to the switch?

More than likely, one of the lower black wires is the hot source, and it is connected to the other lower black to power another box, and is also connected to the existing switch. The upper black was probably also connected to the switch asn was hot when the switch is on and not hot (open) when the switch is off. The whites are all neutrals and all should be connected to each other (and not to the switch).

You can install a double switch or two separate switches in the box to separately control the fan and light. The lower hot black goes to the common on a double switch or one pole on each of the two switches. The upper black goes to the other side of the first switch and the upper red goes to the other side of the second switch. Effectively, these switches share an "in" but have separate "outs".

In the switch box, all of the whites (neutrals) continue to be connected.

At the ceiling box, the white goes to white, the black goes to the wire for either fan or light, and the red goes to the other. The fan wire colors may vary, but the instructions should indicate which is which.

You make no mention of green or bare wire (ground). In a modern, properly wired system, there also should be these, both from each cable and at the fan. Ground wires are connected together and to the base of devices, switches and metal boxes or fixtures. If they are present, connect them. If they are not, you have an ungrounded system that poses a bit of risk if a device is damaged or shorts out.